Method of cleansing metal.



UNITED STATES PATENT OFFICE.

METHOD OF CLEANSING METAL.

Specification of Letters Patent.

Patented Nov. 26, 1907.

Application filed March 26. 1907. Serial No. 864,588.

To all whom it may concern:

Be it known that I, JEAN HAWTHORNE, a citizen of the United States, residing at New York city, New York, have invented certain new and useful Improvements in Methods of Gleansin Metal, of which the following is a clear, ful and exact description.

The object of this invention or discovery is to cleanmetals without undue rubbing or manual work, and I believe that in essence it consists of electro-chemically cleaning the surface of. the article to beo erated upon by converting the oxid or sul d of the metal (which presents a tarnished appearance) into metal. The solution which I use for this purpose is preferably one which will cut or dissolve grease or dirt so that chemical action may uniformly take place on the article, as Well as removing such grease or dirt.

Many difi'erent kinds of 'metal may be cleaned by the selection of the proper electrolyte and electrodes, it being a mere chemists skillthat is required after the underlyin key to the situation is disclosed.

I will describe this invention particularly With reference to the cleaning of gold and silver, premising that other metals such as copper, brass, etc. may be cleansed similarly by the selection of the roper electrolyte and electrode. So far as have gone in my researches, it nowseems to me that the electrolytic action must be one set up by the difference ofpotential existing between the two electrodes of the cell one of which is the article to be cleansed; and I have been unable to secure good results b the use of outside electric potential, but do not limit myself to this preferred method of securing difference of potential for other means may undoubtedly be used for producing the current for this cleansing effect.

Briefly stated, the process for cleaning gold and silver is as follows:

I prefer to use as the anode a receptacle or dish of tin or aluminium, althou h a plate, metal basket or other form of anode may be used. In the receptacle or surrounding the cathode (metal to be cleaned) I place a com parativel weak but hot solution of soda ash, whic in some commercial samples consists of 97% Na CO (sodium carbonate) .7 5% sodium bicarbonate .80% sodium chlorid together with minute traces of other im urities and moisture.

he silver or gold to be cleaned is immersed in this electrolyte and no action will be ap parent while immersed and suspended there-- in (save that action common to soda ash in solution for cleansing grease and dirt), but so soon as a part of the silver or gold touches or is electrically connected with the metal of the vessel, a primary voltaic cell is. produced with the current flowing through the electrolytic solution from the tin or aluminium anode to the silver orfgold cathode. Immediately a transformation will take surface of the silver depending in length of timeupon the strength and temperature of the solution. What occurs to the best of my belief isas follows. Ionic tin 0 'ng a charge is set free in vthe solution. he solution then contains ions of Na, H and S11, all and CO and OH. The H and OH are derived b the dissociation of water. The Ag (silver having a very much less electro- 'lytic solution tension than the Sn tends to collect all the ions in the solution, but the tin ions are not deposited on the silver, because-the re lace (in'the solution), ;those ions lost y the solution. Of these the H gives up its charge and esca es as-molecular hydrogen. The charge ows back to the tin outside of the solution and this 'electrolytic action continues. Now if the silver has upon its surface any tarnish consisting of a sulfid or oxid of silverfthe nascent hydrogen reduces it to metallic silver, apparently without removing any of the silver. This 1s, I be lieve, the chemical ex lanation of the electrochemical part of the c eansing process. There is, as stated before, a certain amount of cleaning due merely to the common action of soda ash upon fat and grease. It will thus be seen that little, (and I have not found that any), of the silver is dissolved or lost, and that no plating effect is produced u on the silver, and though the anode may ose some of its metal, it loses it merely to the solution. It is for this reason that I now believe an outside source of E. M. F. would be impracticable, for with an outside circuit there would be a liability to plate instead of clean the article, which might produce a satisfactory appearance for the time being, but would be disastrous to the article in the long run.

As a general direction I would say that it seems desirable to develop a completely selfcontained electric battery. By self-contained I simply mean that no outside E. M. F. be employed. I use the' article to be place upon the cleaned as a cathode, an anode of an electrolytic solution tension greater than that of the article to be cleaned. The anode enters the solution without attacking or being deposited upon the silver. Acids should not be used to get the best effect. Salts of the anode carrying a charge such as SnCl should not be used on account of their liability to plate the silver with tin, and in the case of silver and old a solution should be employed, suc for example as sodium carbonate; I prefer to use my electrolyte warm, but not undul hot; just warm enough to be comfortab e forthe hands of the individual cleaning the silver. Unless the solution is made undul strong, no un-' comfortable effect -is pro uced upon the hands. After removing an article from the cleansing solution, when the electrolytic action has-brightened its surface, I generally rub it witha soft cloth to remove moisture,

first rinsing it as should be done in all dish washing, in clear warm water.

What I claim is:

1. The process of cleaning tarnished silver which consists in lacing the silver to be cleaned in an alkalin ada ted to set freehydrogen on the surface of the silver, electrically connecting said silver to an anode of greater electrolytic solution tension than said silver, and generating an electro motive force between-said anode and silver solely because of the difference in tension between the same, said anode being capable of passing into the solution during e electrolytic solution the electrolytic action and being there held in solution without lating upon the silver.

2. The process 0 cleaning tarnished silver which consists in selecting a suitable containing vessel of tin, lacing therein a suitable electrol tic solution adapted to set free hydrogen, p acing the silver to be cleaned in said solution in electric connection with said vessel, and generating an electro-motive force between the same solely because of the difl'erence of the solution tension of the two metals, whereb hydrogen is set free on said silver and silver sulfid tarnish on'saidsilvcr is broken down into metallic silver which remains on the surface of the silver.

3. The process of cleaning tarnished silver which consists in selecting a suitable vessel of tin, placing therein a suitable electrolytic solution of sodium carbonate, placing the silver to be cleaned in said solution in electric connection with said vessel, and gen-- erating an electro-niotive force between the same solely because of the difference of the solution tension of the two metals, whereby hydrogen is set free on said silver and silver sulfid tarnish on said silver is broken down into metallic silver which remains on the surface.

Signed at New York city this 25th day of March 1907.

JEAN i -E WTHORN'E. 

